One present means of burning coal cleanly is in a fluidized bed boiler. The coal is burned in a bed of inert material while in a fluidized state, and the heat generated is used to generate and superheat steam, which can be used for producing electricity. Although this is a good means of burning coal cleanly, it does have some other problems. One of the problems is the startup of such a unit, especially with large size units. Coal is difficult to burn in a fluidized bed until the bed of material is raised to a relatively high temperature. Also, care must be taken to protect the heat exchange surface positioned within the bed during startup.